Hi,
Short Version
If you have only Bonjour and iMessages listed then make sure the Bonjour one is Enabled.
You will then be able to use the Windows Menu to see Buddies
However you cannot add Buddies to either Account:-
a) iMessages does not have a Buddy List
b) Bonjour finds Buddies using iChat or Messages on your LAN automatically and adds them to the List.
Long version
Messages and iChat can join the AIM service and various Jabber servers (that in turn can be internetlinked) and at iChat 6 can also join Yahoo.
It is these three account types that support/create Buddy Lists within the app.
Adding AIM, Jabber or Yahoo
In Messages this is in the Messages Menu > Preferences > Accounts and clicking/pressing the + icon below the list.
This opens a new Pane where the top item is a drop down listing AIM then a line, followed by Google and Jabber and another line then Yahoo.
So....
iMessages account in the list is created on first run when you are prompted to add an Apple ID for iMessages uses.
Bonjour is always there for everyone.
AIM, Jabber, Yahoo and Bonjour Accounts have Buddy lists.
You cannot add Buddies to the Bonjour Buddy list as these are found automatically.
Other Macs on your LAN can be found in any Finder Window under Shares by Computer Name.
Messages/Bonjour find other Users on those Macs that are using iChat or Messages with the Bonjour account Enabled.
By Default the Bonjour account is NOT enabled in the Messages > Preferences > Accounts
This in turn means it will not show up in the Windows Menu under "Buddies"
However having a multitude of AIM, Jabber and Yahoo Accounts means the "Buddies" item will appear as in this pic.
The Window Menu lists just "Messages" for the Chat/Interface window and "Buddies" for a combined List.
Unlinking the Accounts in the General section allows the Buddy Lists to be listed separately
I have more accounts then the Keystroke allocation can deal with.
I have shown two Buddy Lists only (Bonjour and one of my AIM ones) with the Preferences at the Bonjour pane in the background.
You will notice the Bonjour Buddy List does not have a + icon lower left.
You cannot Add Buddies (Or Groups) as they are found by the Bonjour process for you. (it adds their Names as they are listed in their Address Book/Contacts app > My Card (You are shown as your Name in your My Card to your Bonjour Buddies).
Therefore to Add Buddies you need either an AIM, Jabber or Yahoo Account (Screen Name or ID you can use with one of these services).
Apple IDs issued by Apple ending in @mac.com, @me.com or @icloud.com are also valid AIM Screen Names (Apple has an Agreement with AIM that they will be recognised).
This may mean your Apple ID is listed for iMessages and then used in the Add Accunt pane as an AIM name.
Google run a Jabber server for Google Mail IDs.
As most Jabber Servers list the server name as the end part of an ID (jabberusername@jabberservername.com becomes jabberservername.com) Google have an issue as they use both @googlemail.com and @gmail.com in their Mail Account IDs.
As a consequence they list another server (talk.google.com) to get around this which leads to the variant split in adding Account.
This means you may need to gain an ID or Screen Name.
This will depend on the Buddies you intend to have.
Essentially it is AIM to AIM and Jabber to Jabber and Yahoo to Yahoo.
As I have said you may already have an valid AIM name in the type of Apple ID you have.
You may have Jabber ID as you have Google Mail Account (you do need to enable "Talk: on your Google Settings)
Facebook also run a Jabber server (you need to enable "Chat" on your account's settings)
I hope this helps
9:07 PM Wednesday; April 17, 2013
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.3)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
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